The invention discloses a robot automatic assembling system based on vision positioning. The robot automatic assembling system comprises an industrial personal computer, a path planning controller, amoving platform, a robot, a robot controller and the like, and the industrial personal computer is connected with the robot controller, a vision system, the moving platform and the like. The moving platform is controlled to transfer the robot to an assembly site; the collected data of the visual system are received and processed, and thus the conversion relationship between the spacecraft coordinate system and the robot base coordinate system is obtained; and then a tail-end actuator is controlled to grab to-be-assembled parts and sends a motion instruction to the robot controller according tothe assembly path given by the path planning controller to control the robot to drive the tail-end actuator to move, and thus automatic assembly of aerospace products is completed. The advantages that operation of the robot is flexible and the working space is large are utilized, the visual system is carried to identify the geometrical features of the mounting position, the detection range is large, positioning accuracy is high, operation is easy and convenient, the response speed is high, and the robot automatic assembling system can be quickly applied to different general assembly stationsof a spacecraft.